High-intensity magnetic separator



Aug. 21, 1951 A. E. PRINCE HIGH-INTENSITY MAGNETIC SEPARATOR 2 Sheets-Sheet 1 Filed Nov. 1, 1946 INVEN TOR. l/wwaii Pwxvce BY (TQM 4770/74 67 Aug. 21, 1 951 A. E. PRINCE 2,565,089

HIGH-INTENSITY MAGNETIC SEPARATOR Filed Nov. 1, 1946 2 Sheets-Sheet 2 llllllliiillll 4.9 "7'27 INVENTOR. 56% i fir/x1? 5/ 0/4 42- BY l I M 9 W G 0 Q Patented Anni, m1v

HIGH-INTENSITY MAGNETIC SEPARATOR Arthur Ernest Prince, Copper cum, Ontario, Canadd, assignor to The International Nickel Company, Inc., New York, N. Y., a corporation of Delaware Application November 1, 1946, Serial No. 707,103 In Canada September 24, 1946 5 Claims.

This invention relates to magnetic separators specially designed to provide an effective magnetic field of high intensity and to be operable in a continuous process to successfully separate magnetic materials and, more particularly, fine and weakly magnetic particles not heretofore satisfactorily recovered in a continuous operation.

The apparatus of the invention is moreover adapted for either dry or wet recovery of metallics as employed for metallic separation in the mining industry. A further important application thereof consists in the recovery of metallics with associated precious metals and iron from ground Bessemer matte in connection with nickel reduction and in the recovery of pyrrhotite with its associated nickel from mill products.

Important features of the present invention include a structural arrangement of the rotary type wherein the material to be separated may be applied directly to the face of the magnets, an improved commutator and circuit control effective to eliminate destructive arcing and thereby to permit employment of high intensity energizing \of the magnets for increased efficiency in fine particle separation and suited for long periods of continuous operation with highly inductive energizing circuits. It moreover includes further novel features of operation and construction materially contributing to higher efficiency in fine and weakly magnetic particle recoveries together with higher rate of separation than has been permitted by the apparatus as heretofore proposed for operations of like character.

The prior art apparatus, as heretofore commercially employed for the separation of magnetic from non-magnetic materials, include rotary and trough and conveyor belt types of separators, the latter having stationary magnets which in practical use have proven successful in the recovery of coarse magnetic materials but, in extensive tests (including varied adjustments as to presentation of feed, density and volume of feed, pulp level, rate of feed movement and belt speed, amount and volume of wash water and current passed through the coils), it has been found that the finer materials, such as present in the Bessemer matte or mill products referred to, werenot satisfactorily recoverable. Even withtwice the normal current applied to the test separators for test purposes, it was found that the improvement in recoveries was extremely slight, the important limiting factor residing in the deficiency of the eil'ective field strength and particularly in the belt type wherein the belt intervenes between the poles Of the magnet and the pulp and further by reason of the tendency to destructive arcing at the commutator contacts in the continuous process apparatus.

As a solution to the problem presented, an object ofthe present invention is to produce a separator of a design and mode of operation adapted for the efficient recovery'of fine and weakly metallic particles in a continuous process.

A further object is to provide a separator of the continuous type providing an intensified and highly efl'ective magnetic field adapted for satisfactory recovery of fine particles and weakly magnetic particles from the mass or pulp.

The invention further provides a separator structure wherein the material to be recovered, in either a dry or wet process is applied or adheres directly to the faces of the magnets to avoid air or space gap losses of the effective field.

It is a further object to produce an apparatus having a circuit control or commutator arrangement adapted for the opening and closing of the energizing circuits to the respective magnets by electronic control prior to and following the intervals of commutator brush gap registration thus to successfully permit of high intensity energizing of the magnets with elimination of destructive arcing at the commutator.

A still further object is to provide a separator having special structural formation of the magnets for more effective separation of the magnetic particles including an advantageous yoke formation operative to concentrate the flux at the core face and desirably associated therewith a shield to prevent magnetic material adhering to the yoke due to splashing of the pulp; the provision of non-magnetic partition plates between the respective magnets for cooling and the provision of pole pieces of special pole face formation conducive to better separation of the finer particles.

It further contemplates an operational arrangement employing a rotary drum structural assembly of the magnets wherein the pulp material is caused to flow over the collector magnet surfaces in counterdirection to the rotative movement of the drum thereby to extend, the effective magnetic area of engagement in the operation and the benefit of increased agitation or flow of the pulp material while subjected to the efiective magnetic flux.

The foregoing and other features and advantages of the present invention will be more fully 3 understood by reference to the drawings wherein like reference characters of the description are applied to the corresponding parts in the several views.

In the drawings:

Fig. l is a vertical sectional view of a rotary separator made in accordance with the invention and wherein the drum structure is shown partially in elevation and partially in section better to show the magnet construction;

Fig. 2 is a view thereof shown in vertical longitudinal section and including a longitudinal view in section of the commutator extensions to the axle of the apparatus;

Fig. 3 is a diagrammatic view showing the energizing and controlling circuit arrangement for the respective magnet coils including diagrammatic showing of the energizing and controlling commutators in exploded arrangement.

In the preferred embodiment of the features of the invention as here shown,the separator apparatus is of the rotary drum type wherein the magnets are supported in a circumferential series upon a cylindrical support mounted to be rotatable upon a central axis and wherein the outer core faces of the magnets are of curvilinear formation conjointly to provide a cylindrical contact and pole surface over which the pulpor mixed magnetic and non-magnetic material is delivered and caused to flow in its travel through the machine for the separation of the magnetic particles by magnetic attraction and adherence to the drum surface.

As shown in Figs. 1 and 2, the support for the magnets is shown at I formed with an outer cylindrical support flange 2 and an inner-bearing sleeve 3 keyed at 5 to a suitably-supported and journalled axle 6 rotated by any conventional gearing connections and driving motor not shown. The axle 6 is formed with a central bore I for wiring connections and with an extended portion 8 for the support of and forming part of a commutator assembly in association with commutator rings and segments mounted thereon. The cores 9 of the magnets are radially disposed in equi-spaced arrangement circumferentially of support I and are secured thereto by the bolts l0. Upon the cores are the coil windings b l to e-4 and, at their outer ends, the cores are formed with pole face enlargements I4 having a curvature concentric with the axis of rotation. The polarity of the magnet coils, when energized, is north outwards and south inwards, and the polarity of all of the magnets are in corresponding arrangement; the operational requirement being that the polarity of the respective magnets shall be in similar arrangement which may be as specified or in the reverse order.

In the preferred structure, non-magnetic strips or partition plates l5 are, as shown, located between the outer poles of the magnets and arranged radially. There are further provided annular side plates or disc flange members I6 of brass or other non-magnetic material attached at their inner margins to the supporting member and likewise attached in close engagement with the side edges of the outer pole pieces [4 and extended radially outward to provide, with the pole faces, guide ways or launders for the reception of the material to be acted upon. The structural arrangement, accordingly, provides a continuous circumferential trough or continuous guide-way; the inner or bottom wall of which is formed by the enlarged magnet faces and outer edges of the partition plates i5 which exten th? full width between the flange member l6 and in close sealing engagement therewith.

The purpose of the partition plates i5 is to provide a cooling fin extending from the pole face inwardly as shown between the coils so as to dissipate the heat generated in the latter. A pulp feed spout I8 is suitably supported for the delivery of the material to be acted upon within the circumferential launder or guide way in the position as shown at an upper point and wherein the material, entering by gravity, is introduced desirably to one side of the central vertical axis, and as indicated in the direction so as to flow downwardly over the collector pole faces at the righthand side of the machine and desirably in the direction counter to the direction of the rotation of the drum which, as indicated by the arrow, is counter-clockwise. In the manner customary to this type of rotary separator, the magnets are energized at one side of the vertical axis and as they progress through the sector wherein the material is flowing by gravity through the launder or guide way channel so that the magnetics may be attracted to and adhere to the pole faces with gravitational separation of the non-magnetics. At the opposite side or sector of the apparatus, the magnets are deenergized by means of a commutator circuit control to permit of separate discharge of the captive magnetic materials at a suitably removed location. In operation, the making and breaking of the magnet energizing circuit may desirably occur substantially at the lowermost or six oclock position and at the uppermost or twelve oclock position, respectively. In customary manner, scrapers l9 and 20 are employed. As shown, they are pivotally supported at 2| and 22 and provided with counterweights operating yieldingly to retain their scraper edges in close engagement with the separator magnet pole surfaces to insure full discharge or removal of the material therefrom. The discharged material from each side of the separator drum drops onto the oppositely-inclined surfaces of a separator or deflector 24 positioned centrally beneath the drum.

In the illustrated embodiment of the invention, the collector pole pieces are of special formation. The pole pieces are of cast iron or steel, and the outer faces are preferably formed with circumferentially extending serrations or ribs 33 which may be directly cast thereon or later machined. When the outer pole face enlargements M are provided with circumferential serrations 33 the scraper edges of scrapers l9 and 20 are provided with corresponding meshing serrations. In operation, the advantage of circumferential serrations, particularly in the treating of a wet pulp, is that the magnetics adhere to the apex portion or points of the ridges or tooth formations leaving the depression of the grooves as in the instance of the embodiment of the features of the invention in an apparatus of the type wherein the lower side of the drum is immersed in a flowing pulp in which case a different design of commutator would be employed to efl'ect a reduced period of energizing which might 5 be in a practical application of substantially 90 of the drum rotation.

Further desirable structural features embodied in the invention include a segmental yoke member 36 of iron or other good magnetic material supported in stationary manner and formed, as best shown in Fig. 2, to provide an iron-clad closed circuit path for the magnetic flux in a manner to concentrate the flux field to pass through the material to the pole faces. To this end, the yoke member 38 is formed with inwardly opposed marginal edges in close spaced relation to the magnet support with a minimum magnetic gap 31 so that the reluctance or air gap resistance may be kept to a minimum. It is outwardly and radially flared from its inner marginal portion and connected by an outer wall it provided on its inner side with a pole extension 39 fitting within the flange member It and of the width substantially corresponding to that of the magnetic pole faces to thereby provide a flux flow path to give additional and effective flux density where needed to make the device more eflicient in the recovery operation and particularly with high intensity energizing. A further increase in available flux could also be obtained by providing electromagnetic windings on the yoke. Supported upon the inner side of the pole extension 39, there is mounted a nonmagnetic shield desirably covering the full area of its projection from the yoke and operating to prevent magnetic material from sticking to the yoke due to splashing of the pulp as it flows from the spout I8. This yoke 36, as indicated in Fig. 1, is of a segmental length extending for substantially 90 and corresponding to the area of magnetic engagement of the material from the point of breaking of the magnet circuit to the point of gravitational discharge of the non-magnetics.

As before referred to, the apparatus is suited for the eflicient separation of dry or wet materials but is found to be particularly efllcient in the connection with the treatment of wet pulp or water-mixed magnetic and non-magnetic materials and operating with high intensity energizing of the magnets. As will be understood to successfully so operate, the structure is assembled with suitable gaskets as required to render the launder or guide-way properly water proofed with relation to the magnet structure enclosed thereby so as to prevent leakage of water or liquid to the inner parts. In operation, the separator drum may be given a rotational speed of approximately'4-15 R. P. M. in the treatment of the specific material as referred to. While the drum may be rotated in either direction, it has been found that important advantage, as referred to, has been obtained in the arrangement wherein pulp or material to be separated travels in the direction opposite to that of the rotation of the drum from which, as will be appreciated, the effective recovery areas are extended and, in addition, a greater agitation of the pulp material is obtained and is conducive to more thorough separation of the finer magnetlcs.

A further and important feature of the invention consists in the provision of a special circuit control and commutator arrangement adapted to permit energizing of the magnet coils by high intensity currents and operable over high intensity current supply by means of cirits related ring or contact segment.

extended periods of use without destructive arcing in the commutator contacts. To this end, the magnet coils are energized from a suitable cults under commutator contact control and including in series with the energizing circuits electron tubes of the 'I'hyratron type having the grids thereof connected to a negative bias supply responsive to the circuit closing of a supplemental and circuit-controlling commutator or rotary switch arrangement having an operating or timing relation to that of the energizing circuit commutator segments to be operable to effect the blocking of the tubes and cessation of energizing circuit current flow prior to gap registration of the energizing circuit commutator brush and to again permit operation of the tubes and closing of the energizing circuit only after-full recontact engagement of the energizing circuit brush with The resulting commutator and circuit control arrangement accordingly provides for de-energizing the magnet circuit before making or breaking of the connections and with short intervals of de-energizingbridging the breaking and re-establishing of the commutator connections.

The circuit controlling arrangement designed to operate in the manner as referred to will be best understood by reference to diagrammatic illustration of Fig. 3. The circuits thereof include energizing circuits from a suitable high intensity current supply or generator and control circuits for the electronic tubes operable in response to a supplemental commutator. The commutators, as shown, are of the conventional split-ring type engaged by suitable brushes for the closing of the circuits and are mounted upon and rotatable with an extension of the drum axle. he commutator arrangement is in two sections composed of the energizing circuit commutator section A and the controlling or supplemental commutator section B. For reference identification of the related commutator rings and magnet coils energized therefrom, the rings are given reference characters from a to 2', and the associated magnet cols are identified by characters 22-! to e-3 and b2 to el wherein the correspondence of the letters indicates their inclusion in related circuits.

In the circuit arrangement as shown, the commutator ring a is a closed ring as customarily employed, and its circuit is common to all of the magnet coils, which, as will be understood, may be varied in number to meet specific conditions and size of apparatus.

The brush 42 of commutator ring a is connected by wire 43 to the neutral of transformer secondary B5. The power supply is a polyphase transformer, or single phase transformer connected to a polyphase source, and operating at conventional power line frequencies, having a secondary winding arranged in the three phase star or Y connection as indicated at 45. This winding could be arranged in a six phase connection with a corresponding increase in number of thyratron tubes employed.

As illustrated, one tube of the various groups 5354--55-58 is connected. to a given transformer lead, it is understood that four separate windings could be employed here to supply power requirements for 53l5-6. However, no difliculty has been experienced in supplying one tube each of 53--456 in parallel from a given transformer lead or phase.

It will be understood that any thyratron or electronic tube conducts current in one direction only, that is, from anode to cathode, so the circuit when any of the tube groups 5345-6 are conducting is from neutral of transformer it-- through secondary windings-each. winding in this case carrying current for 120 time degrees or V3 cycle to tube anodesthrough tubes to cathode to wire 49 and brush 42-to split rings bcd--c of group A, and through one pair of coi1s--for example blb2, to common coils end lead to ring a, brush 42 and to neutral of transformer through wire 43. This current flow is of course direct current.

Groups 53456 are conducting except when any group is made non-conducting due to bias voltage being applied by supplemental commutator B to grids of groups.

When magnet is in operation and rotating the groups 5345-6 with corresponding coil sections b|b2b3-b t, etc., are energized and deenergized in a cyclic manner. As illustrated in Fig. 3 with rotation C clockwise, ring I) is opening coil circuit b ib2 and closing b3b4tubes 53 at that instant being non-conducting due to bias voltage 64 applied to grids through contact making ring f. When tubes 53 again start con ducting, their output current flows through b3--b4 and bi-b2 are de-energized. At the same instant current is flowing from groups 545-6 through coils CiC2--did2 and e|e2. Approximately 45 time degrees later ring C will change from coils CI-CZ to C3-C4 and tube group 54 will be momentarily non-conducting. Rings d-e follow in proper order, thus giving at any given time 180 of magnet face energized and the balance de-energized as one half of any given ring b-c-d-e is connected to a given pair of poles and the other half of given ring is connected to a pair of poles 180 away.

A corresponding group of series of connected tubes 54, 55 and 56, as shown, is connected in series with each of the four energizing circuit segmental rings b, c, d and e by means of the re spective leads 49 and, as shown at 51, suitable resistors are connected in shunt relation to the commutators for circuit protection in absorbing the inductive kick from the coils which, with a D. C. voltage from the Thyratrons, would be severe and might otherwise cause breakdown in some part of the circuit. As will be understood, these resistors may take the form of low voltage lightning arresters of a suitable type.

For satisfactory continuous operation in the control of the energizing circuits, it is necessary that the split in the commutator rings may pass under the commutator brushes without destructive sparking or burning. With the employment, as here contemplated, of high intensity current wherein the D. C. voltage from the Thyratron tubes is of the order of about 250, special provision .is required to eliminate the sparking tendency to insure of long period operation. Provision is accordingly made, by the employment of the tubes and by the grid blocking of the action thereof to break the current flow during the interval of gap and brush registration so that commutation is effected without flashing or sparking. This is effected in the disclosed arrangement by the use of the supplemental commutator or rotary switch arrangement B connected to close circuits from a negative biasing source to the grids of the respective tubes in timed relation or angular displacement to correspond with and bridge over the opening and closing of the respective energizing circuits or brush-gap registrations.

The commutator or rotary switches of the section B consists of oppositely connected contacts 59 separated by-sections of insulating material til and are engaged by the oppositely positioned brushes 62. The latter are included in the grid circuit of the tubes in the arrangement wherein one leg of the circuit is connected to the negative terminal of bias supply battery 54 connected at the positive terminal to the energizing circuit at 63. The other and opposite brush is connected in the opposite leg of the circuit including leads 65 having connection through resistances 66 to the grid electrodes of the tubes in series with each of the secondaries so as to have three phase control. The timing interval or duration of circuit closing engagement by the contacts 59 and brushes 62 is such as to bridge and overlap the time interval of gap engagement of the energizing circuit commutator brushes. As indicated, the angular displacement of the contacts of the commutator or switch I corresponds to the angular position of the gaps of the energizing circuit commutator b and similarly the angular position of the contacts of the switches g, h and i correspond in position to the angularity of gaps of the energizing circuit commutators c, d and e. The disclosed arrangement provides a compact commutator, as one ring takes care of two sets of coils spaced apart thereby requiring only four energizing circuits with associated four groups of series tubes and corresponding number of grid biasing or control circuits controlled by a like number of supplementary commutators or rotary switches 59.

In the operation of the apparatus, as the split in rings, b, c, d, e pass under brushes 42, the coil sections, b-l, b2, cl, c2, d-l, d-2, e-l, and e2 are cut out, and the sections b3, 12-4, c--3, c4, 11-3, 01-4, e3, 6-4 are cut in. As the rings, b, c, d, and e are arranged so that the split between sections occurs at 45 intervals, it will be seen that, at any given time, 180 of the magnetic surface of the drum is energized and the other 180 dc-energized.

In the disclosed arrangement for the control of the energizing circuit by negative biasing of the grid, Thyratron tubes of the F. G. 57 type are employed and are supplied from a polyphase A. C. source as indicated. The latter importantly contributes to successful high intensity operation of the magnets for, as is well known, magnet coils are highly inductive, and a severe ripple voltage limits the amount of available D. C. power. The use of the multiphase plate supply and connected cathodes as shown gives a substantially ripple free D. C. energizing current which, in the instance of the F. G. 5'? tubes, rated at 2.5 amperes each, gives an available power of 7.5 amperes at any voltage from about 50 to 300, the higher voltage being the generally accepted limit for D. C. operation of magnetic separators. While three phase excitation is here shown as an illustrative embodiment of the invention, it will be understood that other multiphase supply sources may be employed as, for instance, a conventional six phase transformer for increase in power and reduction in ripple voltage dependent upon the size and power requirements of the individual separator.

As is further apparent, control grid tubes responsive to positive control could be employed, such as the type known as F. G. 33 with circuit and commutator provisions to normally supply the positive grid bias required for the tube operation. Also, while hot cathode, grid-controlled Thyratron tubes are preferably employed as they are economical to use and replacement is easily accomplished, other types of tubes, such as the pool cathode type, known as ignitrons, could be used to meet higher power requirements.

As will be apparent to those familiar to the art, other and varied modifications may be made therein without departing from the scope of the invention as defined in the appended claims such as, for example, may be required for the embodiment of certain of its features in a machine of the belt conveyor type, rather than that of the rotary drum type as here shown. v

The magnetic separation as described combines features of structure and multiphase energizing with electronic tube circuit control in a manner adapting it to high intensity energizing and more effective separation of the magnetics as required for the separation for fine and weakly magnetic materials including the important operational control of the magnet circuits to be of relatively long time conducting and short time non-conducting at regular intervals with full avoidance of arcing to insure long period op eration. The grid control of the energizing circuits in the arrangement employing constantly heated cathodes further provides for required responsiveness of the tube control at all times for etficient operation.

While the apparatus is suited for both dry and wet separation, it is particularly efficient in the latter operation wherein high efiiciency is obtained bythe employment of the serrations in the magnet pole faces in that the magnetics adhere to the ridges of the tooth formations, and the non-magnetics are readily removed or flushed from the grooves by the fluid, further contributing to high eificiency of operation.

I claim:

1. A magnetic separator comprising a rotary drum provided with a circmnferential series of magnets having core faces arranged to form a cylindrical collector surface for the magnetics,

energizing circuit means for the magnets, commutators operative to open and close the circuit of the respective magnets for segmental energizing of the collector surface, means for rotating the drum, means to deliver the mixed magnetics and non-magnetic material to flow over the energized surface of the drum, a segmental yoke member of magnetic material associated with the magnets during energizing thereof and formed with inwardly directed side extensions substantially coextensive with the magnets to provide a substantially closed outer return path for the fiux and providing a pole extension in spaced relation to the core faces for the passage of the material therebetween and a shield of non-magnetic material on the inward surfaces 01 the pole extensions.

2. A magnetic separator comprising a series of magnets movably supported and having core faces arranged to form a collector surface for the magnetics, energizing circuit means for the magnets, commutators operative to open and close the circuits of the respective magnets for sectional energizing of the collector surface, means for moving the magnets, means to progress the mixed magnetics and non-magnetic material over the energized surface of the magnets, a segmental yoke member of magnetic material associated with the magnets during energizing thereof and formed with side flanges axially coextensive with the magnets to provide a substantially closed path for the flux and pro- Vlding a pole extension in spaced relation to the 10 core faces for the passage of the material therebetween and a shield of non-magnetic material on the inward surfaces of the pole extensions.

3. A magnetic separator for separating magnetic material from non-magnetic material as defined in claim 1 and wherein the magnets are energized from a polyphase A. C. source including in series therewith Thyratron electron discharge tubes connected to the magnet energizing circuits, and having parallel bias supply circuits connected to control electrodes of each of the said Thyratron tubes in an energizing circuit, and a supplemental commutator in the bias supply circuit effective to block the operation of the tubes only at an interval bridging a brushgap registration of the energizing circuit commutator connected therewith whereby the said Thyratron tubes are normally conducting in operation and are de-energized only during the period when the energizing circuits are broken and re-established.

4. A magnetic separator for separating magnetic material from non-magnetic material as defined in claim 1 and characterized by the employment of a polyphase A. C. energizing source including in series with each phase thereof electron discharge tubes having connected cathodes, parallel bias supply circuits connected to the control electrodes of each of the tubes and a supplemental commutator in the bias supply circuits effective to block the operation of the tubes only at an interval bridging the brush-gap registration of the energizing circuit commutator related thereto whereby in operation the tubes are normally conducting and are de-energized only during the period when the connections are broken and re-established.

5. A magnetic separator for separating magnetic material from non-magnetic material as defined in claim 1 and characterized by the magnet energizing circuits being connected to a polyphase A. C. source to provide a substantially ripple-free energizing direct current for the magnets and including in series with each phase thereof multiple magnet coils and grid controlled rectifier tubes having connected cathodes, a bias supply source consisting of a battery having its negative terminal connected to grid bias circuits and its positive terminal to the energizing circuits, parallel bias supply circuits connected to the control bias supply source and to the grids of each of the tubes and a supplemental commutator in the bias supply circuits synchronized to be effective to block the operation of the tubes only at an interval bridging the brush-gap registration of the energizing circuit commutator related thereto whereby in operation the tubes are normally conducting and are de-energized only during the period when the connections are broken and re-established.

ARTHUR ERNEST PRINCE.

REFERENCES CITED Thefollowing references are of record in the 

